Field of Invention
The present invention relates to a dye receiving layer and a method of fabricating the same. More particularly, the present invention relates to a PVC dye receiving layer formed by a lamination process.
Description of Related Art
In recent years, the methods of recording images have been developed. The methods include the uses of ink jet recording, thermal dye transfer, digital photography, silver halide photosensitive material, printing ink and recording pen. Thermal dye transfer has been generally used for high quality and full-color recording. During thermal dye transfer, a dye-donor element including dye layers of yellow, magenta and cyan dyes is heated up, and the dyes vaporize by heating the thermal transfer dyes. The dye layers imprint on the dye receiving element face to face, and the dyes transfer to the dye receiving element (or the dye receiving sheet) by thermal diffusion.
A common dye receiving element (or dye receiving sheet) includes a substrate and at least one dye receiving layer on one side of the substrate. The dye receiving layer includes polymers which can receive dyes by heating the dye receiving layer. During the transfer, the dye at high temperature must move rapidly between the molecules of the dye receiving layer, and the dye remains stable and still in the non-transfer state. Therefore, the selection of the dye receiving layer determines the qualities of images such as ease of printing, light resistance, heat resistance, dye transferability to various chemicals, ease of synthesis, and optical density.
Reference is made to FIG. 1. FIG. 1 illustrates a schematic view of a conventional thermal transfer system. The conventional thermal transfer system includes a heating element 12 and a roller 14 disposed on the opposite side of the heating element 12. During the dye transfer, a ribbon 30 and a photographic paper 20 move along the direction indicated by the arrows. The ribbon 30 (dye-donor element) directly contacts the heating element 12 to prevent the thermal loss of the dyes. The photographic paper 20 is disposed between the ribbon 30 and the roller 14. The photographic paper 20 includes a substrate 22 and a dye receiving layer 24. When the heating element 12 heats the ribbon 30, the dye 26 of the ribbon 30 is heated up and moves rapidly onto the dye receiving layer 24 of the photographic paper 20. The dye 26 is absorbed by the polymers of the dye receiving layer 24.
However, the dyes of conventional thermal dye transfer are limited by the compatibility between the dyes and the dye receiving layer and the various aspects of the process. Only a few polymers meet all the requirement of the method. The common materials used for the dye receiving layer include polyvinyl chloride (PVC) and polycarbonate (PC). Polyvinyl chloride and polycarbonate are generally formed on a substrate by coating. However, the coating requires the use of solvents, and it results in issues such as recycling the solvents and risks of the environmental pollution. The steps of coating process are complicated and thereby increase the manufacturing cost. If the polymers of the dye receiving layer are formed on the substrate by a lamination process, an extra drying process taking a long time is needed because polycarbonate is easy to hydrolyze. The processing temperature of the lamination process is as high as 300° C., and the optical density of polycarbonate is worse than that of PVC. Although PVC has a good optical density as a dye receiving layer, the formation of the dye receiving layer made of PVC on the substrate will easily lead to the non-uniform thickness, the worse surface of the dye receiving layer and many crystal points. This further causes the unevendistribution of the dyes in the dye receiving layer during printing, and finally white dots are formed on the images.